U.S. patent number 5,975,148 [Application Number 09/017,177] was granted by the patent office on 1999-11-02 for papermakers fabric with stacked machine direction yarns forming outer floats and inner knuckles.
This patent grant is currently assigned to Asten, Inc.. Invention is credited to Henry J. Lee.
United States Patent |
5,975,148 |
Lee |
November 2, 1999 |
**Please see images for:
( Certificate of Correction ) ** |
Papermakers fabric with stacked machine direction yarns forming
outer floats and inner knuckles
Abstract
A papermakers fabric, having top and bottom surfaces, woven from
machine direction yarns and one layer of cross machine direction
yarns. The cross machine direction yarns comprise relatively large
and small yarns and the machine and cross machine direction yarns
are arranged such that the machine direction yarns define floats on
one of the surfaces of the fabric and knuckles below the one
surface around small cross machine direction yarns. The parts of
the machine direction yarns defining the knuckles below the one
surface do not extend to the plane of the other surface of the
fabric.
Inventors: |
Lee; Henry J. (Summerville,
SC) |
Assignee: |
Asten, Inc. (Charleston,
SC)
|
Family
ID: |
24567101 |
Appl.
No.: |
09/017,177 |
Filed: |
February 2, 1998 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
640165 |
Apr 30, 1996 |
5713396 |
|
|
|
524800 |
Sep 7, 1995 |
5645112 |
Jul 8, 1997 |
|
|
288158 |
Aug 10, 1994 |
5449026 |
Sep 12, 1995 |
|
|
043016 |
Apr 5, 1993 |
|
|
|
|
855904 |
Apr 13, 1992 |
5199467 |
Apr 6, 1992 |
|
|
534164 |
Jun 6, 1990 |
5103874 |
Apr 14, 1992 |
|
|
Current U.S.
Class: |
139/383A |
Current CPC
Class: |
D21F
1/0036 (20130101); D21F 7/083 (20130101); D21F
1/0054 (20130101); Y10T 442/3114 (20150401) |
Current International
Class: |
D21F
7/08 (20060101); D21F 1/00 (20060101); D03D
013/00 (); D03D 015/00 () |
Field of
Search: |
;139/383A,383AA |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
144592 |
|
Jun 1985 |
|
EP |
|
211426 |
|
Feb 1987 |
|
EP |
|
0259294 |
|
Mar 1988 |
|
EP |
|
273892 |
|
Jul 1988 |
|
EP |
|
0273892 |
|
Jul 1988 |
|
EP |
|
0278769 |
|
Aug 1988 |
|
EP |
|
0580478 |
|
Jan 1994 |
|
EP |
|
2407291 |
|
May 1979 |
|
FR |
|
3426264 |
|
Jan 1986 |
|
DE |
|
537288 |
|
Jun 1941 |
|
GB |
|
1002421 |
|
Aug 1965 |
|
GB |
|
1066975 |
|
Apr 1967 |
|
GB |
|
1362684 |
|
Aug 1974 |
|
GB |
|
2192907 |
|
Jan 1988 |
|
GB |
|
2258249 |
|
Feb 1993 |
|
GB |
|
2292755 |
|
Mar 1996 |
|
GB |
|
12154 |
|
Jul 1996 |
|
GB |
|
9104374 |
|
Apr 1991 |
|
WO |
|
WO01350 |
|
Jan 1993 |
|
WO |
|
Other References
JWI Group's Schedule of Prices; Apr. 15, 1988; with advertisement
of ENERTEX K-2. .
D. Attwood et al.; Drying of Paper and Paperboard; 1972; pp. 68-83.
.
L.H. Bushker and D.C. Cronin; The Relative Importance of Wet Press
Variables In Water Removal; 1992; pp. 25-34..
|
Primary Examiner: Falik; Andy
Attorney, Agent or Firm: Volpe and Koenig, P.C.
Parent Case Text
This application is a continuation of application Ser. No.
08/640,165, filed Apr. 30, 1996, which is a continuation-in-part of
application Ser. No. 08/524,800, filed Sep. 7, 1995, now U.S. Pat.
No. 5,645,112, issued on Jul. 8, 1994 entitled A SINGLE LAYER
PAPERMAKERS FABRICS, which is a continuation of application Ser.
No. 08/288,158, filed Aug. 10, 1994, entitled PAPERMAKERS FABRIC
HAVING FLAT YARN FLOATS, issued on Sep. 12, 1995 as Pat. No.
5,449,026, which is a continuation of application Ser. No.
08/043,016, filed Apr. 5, 1993, entitled PAPERMAKERS FABRIC WITH
STACKED MACHINE DIRECTION YARNS, which is a continuation of
application Ser. No. 07/855,904, filed Apr. 13, 1992, entitled
PAPERMAKERS FABRIC WITH STACKED MACHINE DIRECTION YARNS, issued on
Apr. 6, 1993 as Pat. No. 5,199,467, which is a continuation of
application Ser. No. 07/534,164, filed Jun. 6, 1990, entitled
PAPERMAKERS FABRIC WITH STACKED MACHINE DIRECTION YARNS, issued on
Apr. 14, 1992 as U.S. Pat. No. 5,103,874.
Claims
I claim:
1. A papermakers fabric, having top and bottom surfaces, woven from
machine direction yarns and one layer of cross machine direction
yarns characterized in that the cross machine direction yarns
comprise relatively large and small yarns and the machine and cross
machine direction yarns are arranged such that the machine
direction yarns define floats on one of the surfaces of the fabric
and knuckles below said one surface around small cross machine
direction yarns, wherein the parts of the machine direction yarns
defining the knuckles below said one surface do not extend to the
plane of the other surface of the fabric.
2. A papermakers fabric as claimed in claim 1, wherein machine
direction yarns floating on said one surface of the fabric are made
of the same material to machine direction yarns floating on the
other surface of the fabric.
3. A papermakers fabric as claimed in claim 1, wherein machine
direction yarns floating on one surface of the fabric comprise
polyester.
4. A papermakers fabric as claimed in claim 1, wherein the
relatively large and small cross machine direction yarns are
provided in alternating fashion in said cross machine direction
yarn layer.
5. A papermakers fabric as claimed in claim 4, wherein some of the
machine direction yarns weave with a float over three cross machine
direction yarns and other of the machine direction yarns weave with
a float under three cross machine direction yarns.
6. A papermakers fabric as claimed in claim 5, wherein each machine
direction yarn repeats with respect to four cross machine direction
yarns.
7. A papermakers fabric as claimed in claim 6, wherein the machine
direction yarns are non-circular in cross section.
8. A papermakers fabric as claimed in claim 4, wherein the machine
direction yarns are non-circular in cross section.
9. A papermakers fabric as claimed in claim 8, wherein the machine
direction yarns are flat monofilaments having an aspect ratio of
about 3:1.
10. A papermakers fabric as claimed in claim 1, wherein the inner
knuckles which are defined by each machine direction yarn are
hidden by a corresponding machine direction yarn woven in stacked
alignment in the machine direction.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to papermakers fabrics and in
particular to fabrics comprised of flat monofilament yarns.
2. Description of Related Art
Papermaking machines generally are comprised of three sections:
forming, pressing, and drying. Papermakers fabrics are employed to
transport a continuous paper sheet through the papermaking
equipment as the paper is being manufactured. The requirements and
desirable characteristics of papermakers fabrics vary in accordance
with the particular section of the machine where the respective
fabrics are utilized.
With the development of synthetic yarns, shaped monofilament yarns
have been employed in the construction of papermakers fabrics. For
example, U.S. Pat. No. 4,290,209 discloses a fabric woven of flat
monofilament warp yarns; U.S. Pat. No. 4,755,420 discloses a
non-woven construction where the papermakers fabric is comprised of
spirals made from flat monofilament yarns.
Numerous weaves are known in the art which are employed to achieve
different results. For example, U.S. Patent No. 4,438,788 discloses
a dryer fabric having three layers of cross machine direction yarns
interwoven with a system of flat monofilament machine direction
yarns such that floats are created on both the top and bottom
surfaces of the fabric. The floats tend to provide a smooth surface
for the fabric.
Permeability is an important criteria in the design of papermakers
fabrics. In particular, with respect to fabrics made for running at
high speeds on modern drying equipment, it is desirable to provide
dryer fabrics with relatively low permeability.
U.S. Pat. No. 4,290,209 discloses the use of flat monofilament warp
yarns woven contiguous with each other to provide a fabric with
reduced permeability. However, even where flat warp yarns are woven
contiguous with each other, additional means, such as stuffer
yarns, are required to reduce the permeability of the fabric. As
pointed out in that patent, it is desirable to avoid use of fluffy,
bulky stuffer yarns to reduce permeability which make the fabric
susceptible to picking up foreign substances or retaining
water.
U.S. Pat. No. 4,290,209 and U.S. Pat. No. 4,755,420 note practical
limitations in the aspect ratio (cross-sectional width to height
ratio) of machine direction warp yarns defining the structural
weave of a fabric. The highest practical aspect ratio disclosed in
those patents is 3:1, and the aspect ratio is preferably, less than
2:1.
U.S. Pat. No. 4,621,663, assigned to the assignee of the present
invention, discloses one attempt to utilize high aspect ratio yarns
(on the order of 5:1 and above) to define the surface of a
papermakers dryer fabric. As disclosed in that patent, a woven base
fabric is provided to support the high aspect ratio surface yarns.
The woven base fabric is comprised of conventional round yarns and
provides structural support and stability to the fabric disclosed
in that patent.
U.S. Pat. No. 4,815,499 discloses the use of flat yarns in the
context of a forming fabric. That patent discloses a composite
fabric comprised of an upper fabric and a lower fabric tied
together by binder yarns. The aspect ratio employed for the flat
machine direction yarns in both the upper and lower fabrics are
well under 3:1.
SUMMARY OF THE INVENTION
The present invention provides a papermakers fabric having a system
of flat monofilament machine direction yarns (hereinafter MD yarns)
which are stacked to control the permeability of the fabric. The
system of MD yarns comprises at least upper and lower layers of
yarns. Preferably, each upper MD yarn is paired in a vertically
stacked orientation with a lower MD yarn.
The fabric has a variety of industrial uses. For example, it may be
used as a base fabric for a papermakers wet press felt or as a
dryer fabric. Preferably, multiple layers of stacked CMD yarns are
provided which are maintained in the stacked relationship by the
flat stacked MD yarns to provide suitable void volume within the
fabric. Preferably, three layers of stacked CMD yarns are provided.
In a low permeability embodiment, at least the upper MD yarns are
flat monofilament yarns woven contiguous with each other.
Preferably, the same type and size yarns are used throughout the
machine direction yarn system and both the top and the bottom MD
yarns. Where three layers of CMD yarns are used, the middle layer
CMD yarns are preferably of a smaller diameter than the upper and
lower CMD layer yarns if the fabric is intended to be used as a
press base fabric. For dryer fabrics, the CMD yarns are preferably
all the same.
It is an object of the invention to provide a papermakers fabric
having permeability controlled with woven flat machine direction
yarns.
Other objects and advantages will become apparent from the
following description of presently preferred embodiments.
Other objects and advantages will become apparent to those skilled
in the art after reading the detailed description of a presently
preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a papermakers fabric made in
accordance with the teachings of the present invention;
FIG. 2 is a cross-sectional view of the fabric depicted in FIG. 1
along line 2--2;
FIG. 3 is a cross-sectional view of the fabric depicted in FIG. 1
along line 3--3;
FIG. 4 is a cross-sectional view of a prior art weave
construction;
FIG. 5 illustrates the actual yarn structure of the fabric depicted
in FIG. 1 in the finished fabric showing only two representative
stacked MD yarns;
FIG. 6 is a schematic view of a second embodiment of a fabric made
in accordance with the present invention;
FIG. 6A is a schematic view of an embodiment of a fabric made in
accordance with the present invention.
FIG. 7 is a cross-sectional view of the fabric depicted in FIG. 6
along line 7--7;
FIG. 8 is a cross-sectional view of the fabric depicted in FIG. 6
along line 8--8;
FIG. 9 is a top view of a third embodiment of a fabric made in
accordance with the present invention.
FIG. 10 is a side view of the third embodiment of a fabric made in
accordance with the present invention.
FIG. 11 is a front view of the third embodiment of a fabric made in
accordance with the present invention.
FIG. 12 is a schematic view of the third embodiment of a fabric
made in accordance with the present invention showing only a first
pair of stacked MD yarns.
FIG. 13 is a schematic view of the third embodiment of a fabric
made in accordance with the present invention showing only a second
pair of stacked MD yarns.
FIG. 14 is a schematic view of the third embodiment of a fabric
made in accordance with the present invention showing only a third
pair of stacked MD yarns.
FIG. 15 is a schematic view of the third embodiment of a fabric
made in accordance with the present invention showing only a fourth
pair of stacked MD yarns.
FIG. 16 is a cross sectional view of the fabric depicted in FIG. 9
along line 16--16.
FIG. 17 is a cross sectional view of the fabric depicted in FIG. 9
along line 17--17.
FIG. 18 is a top view of a fourth embodiment of a fabric made in
accordance with the teachings of the present invention.
FIG. 19 is a side view of the fourth embodiment of a fabric made in
accordance with the present invention.
FIG. 20 is a view of the fabric depicted in FIG. 19 along line
20--20.
FIG. 21 is a schematic view of the fourth embodiment of a fabric
made in accordance with the present invention showing four stacked
MD yarns.
FIG. 22 is a schematic view of the fourth embodiment of a fabric
made in accordance with the present invention showing the second
layer of four stacked MD yarns.
FIG. 23 is a cross-sectional view of the fabric depicted in FIG. 18
along line 23--23.
FIG. 24 is a cross-sectional view of the fabric depicted in FIG. 18
along line 24--24.
FIG. 25 is a cross-sectional view of the fabric depicted in FIG. 18
along line 25--25.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment will be described with reference to
drawing figures where the numerals represent like elements
throughout.
Referring to FIGS. 1-3, there is shown a papermakers dryer fabric
10 comprising upper, middle and lower layers of cross machine
direction (hereinafter CMD) yarns 11, 12, 13, respectively,
interwoven with a system of MD yarns 14-19 which sequentially weave
in a selected repeat pattern. The MD yarn system comprises upper MD
yarns 14, 16, 18 which interweave with CMD yarns 11, 12 and lower
MD yarns 15, 17, 19 which interweave with CMD yarns 12, 13.
The upper MD yarns 14, 16, 18 define floats on the top surface of
the fabric 10 by weaving over two upper layer CMD yarns 11 dropping
into the fabric to weave in an interior knuckle under one middle
layer CMD yarn 12 and under one CMD yarn 11 and thereafter rising
to the surface of the fabric to continue the repeat of the yarn.
The floats over upper layer CMD yarns 11 of upper MD yarns 14, 16,
18 are staggered so that all of the upper and middle layer CMD
yarns 11, 12 are maintained in the weave.
As will be recognized by those skilled in the art, the disclosed
weave pattern with respect to FIGS. 1-3, results in the top surface
of the fabric having a twill pattern. Although the two-float twill
pattern represented in FIGS. 1, 2, and 3 is a preferred embodiment,
it will be recognized by those of ordinary skill in the art that
the length of the float, the number of MD yarns in the repeat, and
the ordering of the MD yarns may be selected as desired so that
other patterns, twill or non-twill, are produced.
As best seen in FIGS. 2 and 3, lower MD yarns 15, 17, 19, weave
directly beneath upper MD yarns 14, 16, 18, respectively, in a
vertically stacked relationship. The lower yarns weave in an
inverted image of their respective upper yarns. Each lower MD yarn
15, 17, 19 floats under two lower layer CMD yarns 13, rises into
the fabric over one CMD yarn 13 and forms a knuckle around one
middle layer CMD yarn 12 whereafter the yarn returns to the lower
fabric surface to continue its repeat floating under the next two
lower layer CMD yarns 13.
With respect to each pair of stacked yarns, the interior knuckle,
formed around the middle layer CMD yarns 12 by one MD yarn, is
hidden by the float of the other MD yarn. For example, in FIGS. 1
and 3, lower MD yarn 15 is depicted weaving a knuckle over CMD yarn
12 while MD yarn 14 is weaving its float over CMD yarns 11, thereby
hiding the interior knuckle of lower MD yarn 15. Likewise, with
respect to FIGS. 1 and 3, upper MD yarn 18 is depicted weaving a
knuckle under yarn CMD yarn 12 while it is hidden by lower MD yarn
19 as it floats under CMD yarns 13.
The FIG. 18 upper MD yarns 14, 16, 18, are woven contiguous with
respect to each other. This maintains their respective parallel
machine direction alignment and reduces permeability. Such close
weaving of machine direction yarns is known in the art as 100% warp
fill as explained in U.S. Pat. No. 4,290,209. As taught therein
(and used herein), actual warp count in a woven fabric may vary
between about 80%-125% in a single layer and still be considered
100% warp fill.
The crowding of MD yarns 14, 16, and 18 also serves to force MD
yarns 15, 17, 19, into their stacked position beneath respective MD
yarns 14, 16, 18. Preferably MD yarns 15, 17, and 19 are the same
size as MD yarns 14, 16, and 18 so that they are likewise woven
100% warp fill. This results in the overall fabric of the preferred
embodiment having 200% warp fill of MD yarns.
Since the lower MD yarns 15, 17, 19 are also preferably woven 100%
warp fill, they likewise have the effect of maintaining the upper
MD yarns 14, 16, 18 in stacked relationship with the respect to
lower MD yarns 15, 17, 19. Accordingly, the respective MD yarn
pairs 14 and 15, 16 and 17, 18 and 19 are doubly locked into
position thereby enhancing the stability of the fabric.
As set forth in the U.S. Pat. No. 4,290,209, it has been recognized
that machine direction flat yarns will weave in closer contact
around cross machine direction yarns than round yarns. However, a
3:1 aspect ratio was viewed as a practical limit for such woven
yarns in order to preserve overall fabric stability. The present
stacked MD yarn system preserves the stability and machine
direction strength of the fabric and enables the usage of yarns
with increased aspect ratio to more effectively control
permeability.
The high aspect ratio of the MD yarns translates into reduced
permeability. High aspect ratio yarns are wider and thinner than
conventional flat yarns which have aspect ratios less than 3:1 and
the same cross-sectional area. Equal cross-sectional area means
that comparable yarns have substantially the same linear strength.
The greater width of the high aspect ratio yarns translates into
fewer interstices over the width of the fabric than with
conventional yarns so that fewer openings exist in the fabric
through which fluids may flow. The relative thinness of the high
aspect ratio yarns enables the flat MD yarns to more efficiently
cradle, i.e. brace, the cross machine direction yarns to reduce the
size of the interstices between machine direction and cross machine
direction yarns.
For example, as illustrated in FIG. 4, a fabric woven with a single
layer system of a flat machine direction warp having a
cross-sectional width of 1.5 units and a cross-sectional height of
1 unit, i.e. an aspect ratio of 1.5:1, is shown. Such fabric could
be replaced by a fabric having the present dual stacked MD yarn
system with MD yarns which are twice the width, i.e. 3 units, and
half the height, i.e. 0.5 units. Such MD yarns having a fourfold
greater aspect ratio of 6:1, as illustrated in FIG. 3.
The thinner, wider MD yarns more efficiently control permeability
while the machine direction strength of the fabric remains
essentially unaltered since the cross-sectional area of the MD
yarns over the width of the fabric remains the same. For the above
example, illustrated by FIGS. 3 and 4, the conventional single MD
yarn system fabric has six conventional contiguous flat yarns over
9 units of the fabric width having a cross-sectional area of 9
square units, i.e. 6*(1 u.*1.5 u.). The thinner, wider high aspect
ratio yarns, woven as contiguous stacked MD yarns, define a fabric
which has three stacked pairs of MD yarns over 9 units of fabric
width. Thus such fabric also has a cross-sectional area of 9 square
units, i.e. (3*(0.5 u.*3 u.))+(3*(0.5 u.*3 u.)), over 9 units of
fabric width.
In one example, a fabric was woven in accordance with FIGS. 1, 2
and 3, wherein the CMD yarns 11, 12, 13 were polyester monofilament
yarns 0.6 mm in diameter interwoven with MD yarns 14-19 which were
flat polyester monofilament yarns having a width of 1.12 mm and a
height of 0.2 mm. Accordingly, the aspect ratio of the flat MD
yarns was 5.6:1. The fabric was woven at 48 warp ends per inch with
a loom tension of 40 PLI (pounds per linear inch) and 12.5 CMD pick
yarns per inch per layer (three layers).
The fabric was heat set in a conventional heat setting apparatus
under conditions of temperature, tension and time within known
ranges for polyester monofilament yarns. For example, conventional
polyester fabrics are heat set within parameters of 340.degree.
F.-380.degree. F. temperature, 6-15 PLI (pounds per linear inch)
tension, and 3-4 minutes time. However, due to their stable
structure, the fabrics of the present invention are more tolerant
to variations in heat setting parameters.
The fabric exhibited a warp modulus of 6000 PSI (pounds per square
inch) measured by the ASTM D-1682-64 standard of the American
Society for Testing and Materials. The fabric stretched less that
0.2% in length during heat setting. This result renders the
manufacture of fabrics in accordance with the teachings of the
present invention very reliable in achieving desired dimensional
characteristic as compared to conventional fabrics.
The resultant heat set fabric had 12.5 CMD yarns per inch per layer
with 106% MD warp fill with respect to both upper and lower MD
yarns resulting in 212% actual warp fill for the fabric. The
finished fabric has a permeability of 83 CFM as measured by the
ASTM D-737-75 standard.
As illustrated in FIG. 5, when the fabric 10 is woven the three
layers of CMD yarns 11, 12, 13 become compressed. This compression
along with the relatively thin dimension of the MD yarns reduces
the caliper of the fabric. Accordingly, the overall caliper of the
fabric can be maintained relatively low and not significantly
greater than conventional fabrics woven without stacked MD yarn
pairs. In the above example, the caliper of the finished fabric was
0.050 inches.
It will be recognized by those of ordinary skill in the art that if
either top MD yarns 14, 16, 18 or bottom MD yarns 15, 17, 19 are
woven at 100% warp fill, the overall warp fill for the stacked
fabric will be significantly greater than 100% which will
contribute to the reduction of permeability of the fabric. The
instant fabric having stacked MD yarns will be recognized as having
a significantly greater percentage of a warp fill than fabrics
which have an actual warp fill of 125% of non-stacked MD yarns
brought about by crowding and lateral undulation of the warp
strands. Although the 200% warp fill is preferred, a fabric may be
woven having 100% fill for either the upper or lower MD yarns with
a lesser degree of fill for the other MD yarns by utilizing yarns
which are not as wide as those MD yarns woven at 100% warp fill.
For example, upper yarns 14, 16, 18 could be 1 unit wide with lower
layer yarns 15, 17, 19 being 0.75 units wide which would result in
a fabric having approximately 175% warp fill.
Such variations can be used to achieve a selected degree of
permeability. Alternatively, such variations could be employed to
make a forming fabric. In such a case, the lower MD yarns would be
woven 100% warp fill to define the machine side of the fabric and
the upper MD yarns would be woven at a substantially lower
percentage of fill to provide a more open paper forming
surface.
Referring to FIGS. 6, 7 and 8, there is shown a second preferred
embodiment of a fabric 20 made in accordance with the teachings of
the present invention. Papermakers fabric 20 is comprised of a
single layer of CMD yarns 21 interwoven with a system of stacked MD
yarns 22-25 which weave in a selected repeat pattern. The MD yarn
system comprises upper MD yarns 22, 24 which define floats on the
top surface of the fabric 20 by weaving over three CMD yarns 21,
dropping into the fabric to form a knuckle around the next one CMD
yarn 21, and thereafter continuing to float over the next three CMD
yarns 21 in the repeat.
Lower MD yarns 23, 25, weave directly beneath respective upper MD
yarns 22, 24 in a vertically stacked relationship. The lower MD
yarns weave in an inverted image of their respective upper MD
yarns. Each lower MD yarn 23, 25 floats under three CMD yarns 21,
weaves upwardly around the next one CMD yarn forming a knuckle and
thereafter continues in the repeat to float under the next three
CMD yarns 21.
As can be seen with respect to FIGS. 6 and 8, the knuckles formed
by the lower MD yarns 23, 25 are hidden by the floats defined by
the upper MD yarns 22, 24 respectively. Likewise the knuckles
formed by the upper MD yarns 22, 24 are hidden by the floats of the
lower MD yarns 23, 25 respectively. The caliper of the fabric
proximate the knuckle area shown in FIG. 8, has a tendency to be
somewhat greater than the caliper of the fabric at non-knuckle CMD
yarns 21, shown in FIG. 7. However, the CMD yarns 21 around which
the knuckles are formed become crimped which reduces the caliper of
the fabric in that area as illustrated in FIG. 8. Additionally,
slightly larger size CMD yarns may be used for CMD yarns 21, shown
in FIG. 7, which are not woven around as knuckles by the MD
yarns.
A fabric for use as a dryer fabric was woven in accordance with
FIGS. 6-8, wherein the CMD yarns 21 were polyester monofilament
yarns 0.7 mm in diameter interwoven with MD yarns 22-25 which were
flat polyester monofilament yarns having a width of 1.12 mm and a
height of 0.2 mm. Accordingly, the aspect ratio of the flat MD
yarns was 5.6:1. The fabric was woven at 22 CMD pick yarns per
inch. The fabric was heat set using conventional methods. The
fabric exhibited a modulus of 6000 PSI. The fabric stretched less
than 0.2% in length during heat setting. The resultant fabric had
22 CMD yarns per inch with 106% MD warp fill with respect to both
upper and lower MD yarns resulting in 212% actual warp fill for the
fabric. The finished fabric had a caliper of 0.048 inches and an
air permeability of 60 CFM.
A fabric for use as a base fabric for a press felt was woven in
accordance with FIGS. 6-8 where in the CMD yarns 21 were
constructed of 0.019" and 0.012" in diameter alternating nylon
yarns interwoven with 0.30 mm by 0.90 mm flat nylon machine
direction monofilament yarns. The fabric was woven at 15 to 19
picks per inch for the CMD yarns and 45 to 48 ends per inch for the
MD yarns. A base fabric with higher permeability was woven of the
same design but using 0.30 mm by 0.85 mm flat nylon yarns for the
machine direction yarns instead of the wider 0.30 mm by 0.90 mm
nylon yarns. To complete the press felt, batt material was needled
onto the base fabric in a conventional manner.
The preferred inverted image weave of the lower MD yarns
facilitates the creation of seaming loops at the end of the fabric
which enable the fabric ends to be joined together. In forming a
seaming loop, the upper MD yarns extend beyond the end of the
fabric and the respective lower yarns are trimmed back a selected
distance from the fabric end. The upper MD yarns are then bent back
upon themselves and rewoven into the space vacated by the trimmed
lower MD yarns. When the upper MD yarns are backwoven into the
space previously occupied by the lower MD yarns, their crimp
matches the pattern of the lower MD yarns, thereby locking the
resultant end loops in position. Similarly, alternate top MD yarns
can be backwoven tightly against the end of the fabric such that
loops formed on the opposite end of the fabric can be intermeshed
in the spaces provided by the non-loop forming MD yarns to seam the
fabric via insertion of a pintle through the intermeshed end
loops.
Since the top and bottom machine direction yarns are stacked, the
resultant end loops are orthogonal to the plane of the fabric
surface and do not have any twist. In conventional backweaving
techniques, the loop defining yarns are normally backwoven into the
fabric in a space adjacent to the yarn itself. Such conventional
loop formation inherently imparts a twist to the seaming loop, see
U.S. Pat. No. 4,438,788, FIG. 6.
Referring to FIGS. 9-17, there is shown a third preferred
embodiment of a fabric 150 made in accordance with the teachings of
the present invention which is particularly suited for use as a
base fabric for a press felt. The fabric 150 has upper, middle and
lower layers of cross machine direction yarns 151, 152 and 153,
respectively, interwoven with a system of MD yarns 154 through 161,
which sequentially weave in a selected repeat pattern. The MD yarn
system has upper and lower stacked flat MD yarns that repeat on
four MD yarn pairs 154 and 155, 156 and 157, 158 and 159, and 160
and 161. The MD yarn system interweaves with the three CMD layer
yarns 151, 152 and 153. The stacked pairs of MD yarns repeat with
respect to 12 CMD yarns, 4 from each CMD yarn layer.
The relative stacking of both the MD and CMD yarns is shown in
FIGS. 10-17. The upper layer MD yarns 154, 156, 158, 160 weave
exclusively with the upper and middle layer CMD yarns 151, 152 and,
preferably define interior knuckles under the middle layer CMD
yarns 152 and exterior knuckles over the upper layer CMD yarns 151.
As best seen in FIG. 9, the repeat of the upper MD yarns preferably
define a crow foot pattern with respect to four upper layer CMD
yarns 151, but the MD yarns may be ordered to define a regular
twill pattern.
The lower layer MD yarns 155, 157, 159, 161 weave in a similar
manner as upper layer MD yarns, but with respect to the middle and
lower CMD yarn layers 152, 153. The lower layer MD yarns 155, 157,
159, 161 weave such that interior knuckles are defined by the lower
MD yarns 155, 157, 159, 161 over the middle layer CMD yarns 152
which are vertically aligned with the exterior knuckles defined by
the upper MD layer yarns 154, 156, 158, 160 over the upper layer
CMD yarns. Similarly, the lower layer MD yarns 155, 157, 159, 161
weave exterior knuckles under lower layer CMD yarns 153 which are
vertically aligned with the interior knuckles which are defined by
the upper MD layer yarns 154, 156, 158, 160 under the middle layer
CMD yarns 152.
A press felt base fabric produced in accordance with the third
embodiment shown in FIGS. 9-17 is preferably woven 15-19 CMD yarns
per inch in each layer using 0.5 mm diameter nylon yarns for the
upper and lower CMD layers and 0.3 mm diameter nylon yarns for the
middle CMD layer. The fabric is preferably woven at 45-48 MD yarns
per inch in either a low permeability or a high permeability
version. In the low permeability version, 1.06 mm wide by 0.25 mm
high nylon MD yarns are used to produce a base fabric permeability
in the range of 90-200 CFM. In the high permeability version 0.85
mm wide and 0.30 mm high nylon MD yarns are used to produce a base
fabric permeability in the range of 200-400 CFM.
To form a press felt, batting is needled onto the woven base fabric
in a conventional manner having a weight in the preferred range of
2.2-2.6 oz/sq. ft. Preferably, a batt weight of 2.3 oz/sq. ft. is
used.
A dryer fabric produced in accordance with the third embodiment
shown in FIGS. 9-17 is preferably woven 15-19 CMD yarns per inch in
each layer using 0.5 mm diameter polyester yarns. The fabric is
preferably woven at 45-48 MD yarns per inch from 1.06 mm wide by
0.25 mm high polyester MD yarn to produce a base fabric
permeability in the range of 90-200 CFM.
Referring to FIGS. 18-25, there is shown a fourth alternate
embodiment of a papermakers fabric 110 which is also particularly
suited for use as a press felt base fabric. The fabric 110 has
upper, middle and lower layers of CMD yarns 111, 112, 113,
respectively, interwoven with a system of machine direction MD
yarns 114-121 which weave in a selected repeat pattern. As best
seen in FIGS. 21-25, the MD yarns system repeat is defined by a
first group of stacked MD yarns 112-117 and a second group of
stacked MD yarns 118-121 which repeat with respect to 12 CMD yarns
111-113, four yarns from each of the upper, middle and lower CMD
yarn layers.
The MD yarn system includes an upper interior MD yarn layer defined
by MD yarns 115,119 which weave exclusively with the upper and
middle CMD layer yarns 111, 112 forming knuckles over alternate
upper layer CMD yarns 111 and under alternate middle layer CMD
yarns 112. Upper interior MD yarns 115, 119 both weave between
alternate pairs of upper and middle layer CMD yarns 111, 112 within
the fabric repeat.
The MD yarn system also includes a lower interior MD yarn layer
defined by MD yarns 116, 120 which weave exclusively with the
middle and lower CMD layer yarns 112, 113 forming knuckles over
alternate middle layer CMD yarns 112 and under alternate lower
layer CMD yarns 113. Lower interior MD yarns 116, 120 both weave
between alternate pairs of middle and lower layer CMD yarns 112,
113 within the fabric repeat.
The knuckles defined by the upper interior and lower interior MD
yarn layers are vertically aligned in a manner similar to the upper
and lower MD yarn layers of the embodiment disclosed in FIGS.
9-17.
The MD yarn system also includes an upper face MD yarn layer
defined by MD yarns 114, 118 which weaves exclusively with the
upper layer CMD yarns 111 with a float over three and a knuckle
under one of the upper layer CMD yarns 111 within the repeat. The
knuckles defined by upper face layer yarn 114 being vertically
aligned with the knuckles defined by the upper interior MD yarn 115
under middle CMD layer yarns 112; the knuckles defined by upper
face layer yarn 118 being vertically aligned with the knuckles
defined by upper interior MD yarns 119 under middle CMD layer yarns
112.
The MD yarn system also includes a lower face MD yarn layer defined
by MD yarns 117, 121 which weaves exclusively with the lower layer
CMD yarns 113 with a float under three and a knuckle over one of
the lower layer CMD yarns 113 within the repeat. The knuckles
defined by lower face layer yarn 117 being vertically aligned with
the knuckles defined by the lower interior MD yarn 116 over middle
CMD layer yarns 112; the knuckles defined by lower face layer yarn
121 being vertically aligned with the knuckles defined by lower
interior MD yarns 120 over middle CMD layer yarns 112.
As a result of the repeat pattern alternate CMD yarns in each CMD
yarn layer are crimped to a significantly greater degree to the
weaving of knuckles by the MD yarns system as best seen in FIGS.
21, 22 and 25. None of the MD yarns weave knuckles about the other
alternate CMD yarns of each of the upper middle and lower CMD layer
111, 112 and 113. Accordingly, a balanced weave similar to the
balanced weave described with respect to the single CMD layer
embodiment illustrated above is defined in a multi CMD layer
fabric. It will be recognized to those of ordinary skill in the art
that the MD yarn system could include four groups of stacked MD
yarns within the repeat to define either a twill or broken twill
surface pattern. However, as illustrated above only two groups of
MD yarns 114-117 and 118-121 are required for the fabric's
preferred construction.
A press felt base fabric produced in accordance with the fourth
embodiment shown in FIGS. 18-25 is preferably woven 15-19 CMD yarns
per inch in each layer using 0.5 mm diameter nylon yarns for the
upper and lower CMD layers and 0.3 mm diameter nylon yarns for the
middle CMD layer. The fabric is preferably woven at 90-96 MD yarns
per inch in either a low permeability or a high permeability
version. In the low permeability version, 1.06 mm wide by 0.25 mm
high MD nylon yarns are used to produce a base fabric permeability
in the range of 90-200 CFM. In the high permeability version 0.85
mm wide and 0.30 mm high MD nylon yarns are used to produce a base
fabric permeability in the range of 200-400 CFM.
The addition of upper and lower face MD yarn layers does not
substantially effect the fabric's permeability in contrast with
fabrics made in accordance with the third embodiment depicted in
FIGS. 9-17. The floats of the upper and lower face layer MD yarns
provide a smoother support surface, but the inclusion of those
yarns does not reduce the void volume of the base fabric in
contrast with fabrics made in accordance with the third embodiment
depicted in FIGS. 9-17.
To form a press felt, batting is needled onto the woven base fabric
in a conventional manner having a weight in the preferred range of
2.2-2.6 oz/sq. ft. Preferably, a batt weight of 2.3 oz/sq. ft. is
used.
In the preferred low permeability embodiment, the upper face MD
yarns 114 and 118, are woven contiguous with respect to each other.
This maintains their respective parallel machine direction
alignment and reduces permeability. Such close weaving of machine
direction yarns is known in the art as 100% warp fill as explained
in U.S. Pat. No. 4,290,209. As taught therein (and used herein),
actual warp count in a woven fabric may vary between about 80%-125%
in a single layer and still be considered 100% warp fill.
The crowding of MD yarns 114 and 118 also serves to force MD yarns
115-117 and 119-121, into their stacked position beneath respective
MD yarns 114, 118. Preferably MD yarns 115-117 and 119-121 are the
same size as MD yarns 114 and 118 so that they are likewise woven
100% warp fill. This results in the overall fabric of the preferred
low permeability embodiment having 400% warp fill of MD yarns.
A dryer fabric produced in accordance with the fourth embodiment
shown in FIGS. 18-25 is preferably woven 15-19 CMD yarns per inch
in each layer using 0.5 mm diameter polyester yarns. The fabric is
preferably woven at 90-96 MD yarns per inch from 1.06 mm wide by
0.25 mm high polyester MD yarn to produce a fabric having a
permeability in the range of 90-200 CFM.
While the present invention has been described in terms of the
preferred embodiment, other variations which are within the scope
of the invention as defined in the claims will be apparent to those
skilled in the art.
* * * * *